The present invention relates to a manufacturing method of a semiconductor device, and in particular, to a technique effective when applied to a manufacturing method of a semiconductor device including the step of attaching semiconductor wafers together.
In the step of forming a backside illumination CMOS (Complementary Metal Oxide Semiconductor) image sensor that is one type of image pickup devices to be used in digital still cameras, etc., it is known that, as a method of making up for the strength of a semiconductor wafer (semiconductor substrate) over which a device (semiconductor element) is formed, another semiconductor wafer is attached to the semiconductor wafer.
Patent Document 1 (Japanese Unexamined Patent Publication No. 2011-243959) describes that: before substrates are attached together, the surfaces of the substrates are cleaned by a wet treatment; and after a plasma treatment is performed on the surfaces thereof, a heat treatment is performed on the substrates. Patent Document 1 also describes that the substrates are attached together in a treatment chamber having a reduced pressure. However, it does not describe that the substrates are attached together in a state where the temperatures of the substrates are made to be room temperature (normal temperature).
Patent Document 2 (Japanese Unexamined Patent Publication No. 2009-4741) describes that: before and when substrates are bonded together, the substrates are placed in vacuum; and the organic components in the adhesive layer between the substrates are removed by heating the substrates in vacuum when the substrates are bonded together. However, it does not describe that the substrates are attached together in a state where the temperatures of the substrates are made to be room temperature (normal temperature).